Although it doesn't add too much to the story line, FEAR 3 is a great shooter that is very fun and challenging in some parts. Enemy AI is smart enough to keep you interested without frustrating you, weapons have been redsigned and are very fun to use.
Co-op play is a great addition and i highly recommend it. Single player is still very entertaining, playing through the game as Point Man and then as Fettel is a very nice contrast, so the game has some replay value
The biggest fault in the game is that it isn't scary, which is something that i loved about FEAR 1 and had mixed feelings on in FEAR 2. The scariest parts of this game is getting swarmed by a gauntlet of monsters, which if you are good at shooters, is more annoying than scary.
FEAR 3 is a very good entry in the series and i hope that if there is a sequel, it is made in a similar style to FEAR 3 but with scares similar to FEAR 1.